Water Vapor and Gravity Act Together to Warm the Earth

It is commonly said that greenhouse gases cause the Earth's surface temperature to be 33K warmer than it would be without these infrared-active gases.  This is based on the idea that the total solar insolation presently absorbed by the Earth, both surface and atmosphere, would all be emitted from the surface as thermal radiation and emitted directly to space if there were no greenhouse gases in the atmosphere. Using the Stefan-Boltzmann Law for thermal radiation, the surface temperature is then said to be 255 K.  No correction is made for the fact that without greenhouse gases, the solar radiation lost to space by reflection would be less.  There is no correction either for the fact that most of the solar radiation absorbed by the atmosphere would be absorbed by the surface instead.  Let us make these corrections here to derive a more realistic total greenhouse gas effect as a starting point for understanding how water vapor and gravity together cause the Earth to be as warm as it is.

Reference is made to two NASA Earth Energy Budget diagrams to determine the reflections from the atmosphere, clouds, and the surface:

Despite the long-standing claim that the science is settled, it is interesting to note that these two NASA energy budgets, representing the settled science as they do, do not agree.

The first one says the sum of the solar radiation reflected by the atmosphere and clouds is 23%, while the second one says that sum is 26%.  The first one says the surface reflection is 7%, while the second one says it is 4%.  The first one says that 48% of the incoming solar radiation is absorbed by the surface, while the second one says that 51% is absorbed.  The first NASA energy budget says that 23% of the solar radiation is absorbed by the atmosphere and does not separate out the percentage absorbed by clouds.  The second energy budget says the sum of the incoming solar absorbed by the atmosphere and clouds is 19%.  Let us bear these differences in mind as we look at the following NASA Earth Energy Budget that states that the Earth is warming due to 0.6 W/m² , which is only 0.18% of the incoming solar radiation.  With several percentage differences in the long settled science, it is fascinating that NASA can peer through the uncertainties to see a warming Earth due to only 0.18% of the solar radiation.  Among other things, NASA makes the claim that this 0.18% is not due to changing solar output.

In the third NASA energy budget, the solar radiation reflected by clouds and atmosphere is 22.6% and that reflected from the surface is 6.7%, in close agreement with the first energy budget.  Now the problem is that a portion of the reflection from the atmosphere is due to reflection off nitrogen and oxygen molecules.  Some is also due to reflection off haze due to water vapor.  To estimate the added solar insolation absorbed by the surface when greenhouse gases are eliminated from the atmosphere, it is necessary to know the reflection from haze, which would not exist but for water vapor.  There is no certain value for the added solar radiation incident on the surface and no agreement among the three diagrams on the fraction of that which will be reflected.  Such is the settled science.  I will work with an estimate that 22% of the top of the atmosphere solar radiation is added to that incident on the surface in the case of no greenhouse gases.  I will then assume that of the solar radiation incident on the surface, 12.3% is reflected.  This value is from the third diagram where 22.9/(22.9 + 163.3) = 0.123.

22% of 340.4 W/m² is 74.9 W/m² , which is all but 2.1 W/m² of the 77.0 W/m² reflected into space from the atmosphere in the third diagram.  The 77.1 W/m² adsorbed by the atmosphere in that diagram does not happen with no greenhouse gases either. Consequently, the solar radiation incident on the surface is increased to 338.3 W/m² .  Of this, 12.3% is reflected, so 296.7 W/m² is adsorbed by the surface.  This is 133.4 W/m² more than the 163.3 W/m² adsorbed by the surface in the third NASA Earth energy budget and 56.8 W/m²  more than is now absorbed by both the atmosphere and the surface.  This is no small addition to the absorbed energy, though proponents of the catastrophic man-made global warming hypothesis frequently claim that greenhouse gases have little effect on adsorbed solar radiation.  Some will say that I have no business removing the reflection from clouds, but I cannot understand how one can have clouds without the most important greenhouse gas of all, namely water vapor.

Applying the Stefan-Boltzmann equation we have for the surface temperature with no greenhouse gases:

P (W/m²) = 296.7 W/m² = σ T⁴ = (5.6697 x 10^-8 W/m²K⁴) T⁴, so T= 269.0 K,

which is only 19.0K less than 288.0 K, not the usually quoted 33K less.  The original greenhouse effect is only 19.0/33.0 = 0.576 times the scale we are usually told it is.  This is one of the means by which it is exaggerated in the settled science.

The role of water vapor is huge.  Gravity creates a gradient in atmospheric gas molecule kinetic energies and therefore in their temperature.  This gravity-induced temperature gradient will not have a large effect on the surface temperature unless there is a large atmospheric emission of energy to space from a substantial altitude.  Water vapor is the primary provider of both the required energy at substantial altitudes in the atmosphere.  It helps that the concentration of water vapor in the atmosphere falls off rapidly in the upper troposphere, so that water vapor with its relatively wide range of radiating frequencies can readily radiate most of the Earth's adsorbed solar radiation from the upper troposphere into space.

Water vapor critically reduces the direct emission of surface emitted thermal radiation to space.  In summary, it does this in three key ways:

• Water vapor absorbs most of the two-thirds of the surface thermal emission of infrared radiation that is absorbed in the atmosphere. Carbon dioxide and the other infrared-active gases also participate in this function as minor partners.

• The creation of water vapor reduces the surface emission of infrared radiation at the surface as a competing surface cooling mechanism by soaking up heat in the process of water evaporation.  This is a result of energy conservation.  Energy that goes into evaporating water cannot also go into photon emission. Carbon dioxide plays no role in this mechanism at all.

• The condensation of water vapor at substantial altitudes in the troposphere provides a large store of energy to be radiated from the upper troposphere into space.  There is no corresponding role for carbon dioxide.

The fact of the large emission of radiation by infrared-active molecules at the top of the troposphere also allows thermals to come into play as a means of reducing surface radiation emission and as a feed of energy to the upper troposphere from whence it can be radiated into space.  It is then this radiation to space from the upper troposphere that determines the temperature of the upper troposphere.  This in turn allows the gravitational temperature gradient to increase the surface temperature relative to the temperature of the upper troposphere from which most of the Earth's thermal radiation into space is emitted.

Without greenhouse gases, the gravity-induced temperature gradient still exists, but the temperature anchor has to be the Earth's surface since it is the only possible source for thermal radiation to space.  The infrared-active gases do provide substantial warming of the Earth's surface, but contrary to the usual claim that it is due simply to absorbing surface emitted thermal infrared in the atmosphere, it is really due to all three of the bulleted mechanisms above.  Only water vapor plays a role in two of the three critical mechanisms and it is very dominant in the remaining mechanism. When this is understood, it is clear that water vapor is a much more dominant actor in the warming of the Earth than is recognized in the general settled science viewpoint.  When only the first bulleted mechanism is said to be the reason for a warmer Earth, carbon dioxide seems to play a bigger role than it really does.

The partnership of water vapor with the temperature gradient in the atmosphere due to gravity provides us with a much warmer Earth.  This partnership is completely lost in the so-called settled science.  To learn more about the gravity induced temperature gradient in the troposphere, see mgh, Not Just Greenhouse Gases, Provides a Warm Earth.  When the water vapor and gravity partnership is properly understood, the very minor role of carbon dioxide is better understood.  When that is understood, the wrongheadedness of catastrophic man-made global warming is understood.